This invention relates to a toroidal continuously variable transmission for a vehicle, in particular relates to improvements in a power roller sandwiched between an input disk and an output disk.
The power roller of a toroidal continuously variable transmission is sandwiched between an input disk and an output disk so as to transmit the rotations of the input disk to the output disk. The structure of such a power roller is disclosed in JP-A-7-229549 published by the Japanese Patent Office in 1995.
The power roller comprises an inner roller which makes contact with the input and output disks and an outer roller which supports a load applied on the inner roller through a ball bearing. A through hole is provided on the central axis of the inner roller to allow insertion of pivot shaft of a trunnion. Therefore the problem has arisen that when a large load is applied by the input and output disks, the inner roller displays a tendency to undergo compression deformation inwardly.
This deformation results in a deterioration in component durability and hinders the smooth transmission of a rotation torque by the power roller.
The present invention is proposed to solve the above problem and has the object of avoiding deformation of the inner roller of the power roller and maintaining smooth rotational motion.
A further object of this invention is to increase the durability of the power roller.
In order to achieve the above objects, the invention provides a toroidal continuously variable transmission which comprises an input disk and an output disk disposed co-axially in an opposed orientation, a power roller which is sandwiched in order to transmit drive force between the input and output disks, and a trunnion which supports the power roller to rotate freely on a pivot shaft. The power roller comprises an inner roller making frictional contact between the input and output disks and an outer roller supporting a contact load input from the input and output disks to the inner roller through a ball bearing, and an inner radial hole to support a pivot shaft is formed on a rotational center of the inner roller, the inner radial hole being formed as a recessed hole that opens toward the outer roller and a bottom part of the inner radial hole is substantially closed on a side that faces the input and output disks.
The details as well as other features and advantages of the invention are set forth in the remainder of the specification and are shown in the accompanying drawings.